Hello, I just started with boost and it is obvious that I do not understand give my compiler (not mentioning code::blocks) the correct instructions. I installed boost_1_61_0 on Ubuntu 14.04 and followed the instruction. So I did (as root after sudo -i) in the directory of boost_1_61_0. I use g++4.9. It was the same with g++4.8. 1) ./bootstrap.sh prefix=/usr/local 2) ./b2 install So the libs are: /usr/local/lib The headers: /usr/include/boost Actually I was interested in some stuff with asio. So I started with this code from the tutorial. http://www.boost.org/doc/libs/1_61_0/doc/html/boost_asio/tutorial/tutdaytime... g++ -Wall main.cpp -o zclient /tmp/ccxx7PrW.o: In Funktion `__static_initialization_and_destruction_0(int, int)': main.cpp:(.text+0x52e): Nicht definierter Verweis auf `boost::system::generic_category()' main.cpp:(.text+0x53a): Nicht definierter Verweis auf `boost::system::generic_category()' main.cpp:(.text+0x546): Nicht definierter Verweis auf `boost::system::system_category()' /tmp/ccxx7PrW.o: In Funktion `boost::system::error_code::error_code()': main.cpp:(.text._ZN5boost6system10error_codeC2Ev[_ZN5boost6system10error_codeC5Ev]+0x17): Nicht definierter Verweis auf `boost::system::system_category()' /tmp/ccxx7PrW.o: In Funktion `boost::asio::error::get_system_category()': main.cpp:(.text._ZN5boost4asio5error19get_system_categoryEv[_ZN5boost4asio5error19get_system_categoryEv]+0x5): Nicht definierter Verweis auf `boost::system::system_category()' /tmp/ccxx7PrW.o: In Funktion `boost::asio::detail::posix_thread::~posix_thread()': main.cpp:(.text._ZN5boost4asio6detail12posix_threadD2Ev[_ZN5boost4asio6detail12posix_threadD5Ev]+0x26): Nicht definierter Verweis auf `pthread_detach' /tmp/ccxx7PrW.o: In Funktion `boost::asio::detail::posix_thread::join()': main.cpp:(.text._ZN5boost4asio6detail12posix_thread4joinEv[_ZN5boost4asio6detail12posix_thread4joinEv]+0x2b): Nicht definierter Verweis auf `pthread_join' /tmp/ccxx7PrW.o: In Funktion `boost::asio::detail::posix_thread::start_thread(boost::asio::detail::posix_thread::func_base*)': main.cpp:(.text._ZN5boost4asio6detail12posix_thread12start_threadEPNS2_9func_baseE[_ZN5boost4asio6detail12posix_thread12start_threadEPNS2_9func_baseE]+0x29): Nicht definierter Verweis auf `pthread_create' collect2: error: ld returned 1 exit status I have to add that the simple programm in the starting guide worked properly http://www.boost.org/doc/libs/1_61_0/more/getting_started/unix-variants.html... via g++ -Wall main.cpp -o zu It worked in Code::Blocks as well (without any additional information). Even the second simple programm (same link) I managed to compile giving the full path: g++ -Wall main.cpp -o extractmail /usr/local/lib/libboost_regex.a At no time I had not to instruct the compiler about the headers. I was wondering. So it must have anything to do with the libs. Coming back to my asio- example. Do I need libs for it? I guess is has something to do with the expression -lboost_system. I used it without understanding it. But it did not help. Actually I would appreciate if was able to use Code::Blocks but I did not manage to give Code::Blocks the correct instructions. I found some hints, at least amounts of hints ... But it did not work at all. If somebody is able to explain it (for idiots) ... This would be great. Thanks Hermann